Method for the production of titanium



2,857,264 Patented .Oct. 21, 1958 METHOD FORTHE .PRQDUCTIONv OF'TITANIUIVI Fredric. V. Schossherger, Hinsdale, 111., assignor to Armour: Research Foundation of Illinois Institute of Technology, Chicago, Ill -a corporation of'lilinois No Drawing. Application February 8,1957 Serial N0..638;898

8' Claims. (c1. 75,84.5)

This invention relates. to a method of producing titanium from titanium bearing tores and other. titanium bearing materials.

More particularly it relatesto such method -wher eby,.suchores and materials are'first converted to dry alkali chlorotitanates which are then reduced to metallic titanium. Alkali: metal reducing agents are utilized for the latter reduction. Specifically my invention encompasses a novel procedure whereby solutions of titanium as derived from suchfltitanium bearing materials :are conveniently converted. to titanium metal.

In recent years .the need for titanium has greatly increased because of its unique properties and those of its alloys. Because of its comparatively low weight, corrosic-n-resistance and high-strength the uses of titanium are being multiplied daily. One great drawback to the use of titanium up to the present time has been the difficulty with which it is produced in commercial form with a consequent high price. Suchhigh price has been a deterrent to the wide-spread use of the metal.

Although many disclosures have been made showing how to produce titanium," to my knowledge all these disclosures eithercontemplate improvements to the basic Kroll process,- shown in U. S. Patent No. 2,205,854, a process which is primarily the'magnesium reduction of titanium tetrachloride in a'bomb-like container, or the Van'Arkel iodide process. All such processes developed until the advent of the instant invention are limited to titanium production in a discontinuous batch manner. The raw materials are placed in a batch reactor, the process is carried out, and the metal is then separated from the receptacle. In many cases because of local overheating such separation is tedious and expensive. Although these aforementioned procedures could satisfy the limited demands for titanium of the past, our present stage of techno-logical development and readily foreseeable demands of the future make it essential that a simple, relatively inexpensive and continuous process for titanium production be developed and it is to this end that the instant invention isdirectedj In the past titanium has been produced primarily from titanium tetrachloride and said tetrachloride has in turn been made from high-grade, expensive rutile ores. The use of rutile was necessary because of the complexities and high cost of removing the impurities resulting from use of lower quality ores. In my invention, on the other hand, although rutile may be used, the cheaper titanium ores such as ilmenite (FeTiO iron containing titanium slags or any other titanium bearing materials are readily converted into pure titanium metal. Thus, as will be shown below, not only is my process continuous but also less expensive in terms of raw materials and manufacturing costs.

Underlying the instant invention-is my discovery that moist potassium chlorotitanate, specifically, and other alkali chlorotitanates more generally, may be dried to a fine powder by treatment with hydrogen chloride gas whilegheatedin the temperature rangefrom about 207 C.

to about 300 C. This; removes all but va minutefrao tion of thelwateror'rnother liquor present in thesolid chlorotitanate particles. Inaccordance with the proce ,dure set out fully below, once dry alkali chlorotitanateis obtained it is readily-reduced to metallic titanium'while salts of other'elements. originally,present-in the starting material are produced. The metal obtained by;-reduct ion of such dry alkali, chlorotitanate is ;quite acceptable for industrial uses and is at least as pure as the standard; commercial titanium presently available.

Anobject of the-instant invention is to provide-a .continuous method of; producingtitanium.

Another object of the: instant invention -is;, to provide a method o-fproducingifianium: from all available sources thereof and particularlyjlmenite.

Still, another object of the instant invention is; to; provide a method of producing titanium from; titanium solutions.

Yet anotherobjeet oftthe :instant invention is to. produce titanium of commercial quality-by the reduction of dry potassium chlorotitanate, and dry. alkali chlorotitanates more generally withv alkali metal reducing. agents.

A further object of the-instant. invention is to produce titanium under farless severe operating, conditionsof temperature and-pressure than hithertoforeknown.

Before entering upon adetailed explanation of; my process it should beunderstood that such processconsists of two primary steps; first the: production :o-f dry alkali ohlorotitanates from titanium bearing materials and second the reduction: of such alkal chlorotitanates to-yield titanium. Instep .one the raw material is dissolveduin an acid solution; converted to a halide; precipitated, and dried. In step two reduction of the chlorotitanaterand separation :ofthe end-products are accomplished;

It is well known that titanium ores and-many-other titanium bearing materials may. be dissolved in: sulfuric acid :or a combinationofsulfur-io and hydrochloric acids as the initial step. in thereco-veryof titanium compounds from such materials. After such solution has beenmade the novel features of my'inventionmaybe utilized to; recover pure titanium metal.

It should be understood that my invention is operable with substantially all titanium solutions. Since the making of such solutions for the manufacture of titaniumdioxide pigments is old in the-art, reference will be had. only to those factors in the prior art necessary to place the instant invention improper perspective. Thus to'be more exact whilea complete procedure isdisclosed herein only the concepts deemed novel are elaborated upon andfully considered.

In order that myinventionmay befully understoodthe following example of theprocess is presented:

llmenite ore .is'firstground-to 250 mesh and ithe par.- ticles mixed with sulfuric acid (66 Baum). Thezilmenite acid mixtureis heated rapidlyto'from-approximately 80 totlZO" C. This heatinginitiatesan exothermic reaction which maintains the'temperature at theaboverange -:until solidification or caking ofthe reaction .product occurs. The solidifiedmassis nextleached-with either dilute sulfuric acid-or a mixture of sulfuric and hydrochloric :aci'd-s. Such acid mixture may be obtained by therecycling of acidic solutions from other steps in the process: The leaching step produces an .acidsolution of titanium and iron having additional insolublematerial suspendedthere. in, which insoluble material is readilyseparated fromrthe titanium-iron solution by filtration or a like procedure.

It is now necessary to removethe iron from the solotion. Approximately 70% of such iron present maypbe crystalleded out in the form of iron sulfate merely by cooling the solution to a point where iron sulfate crystals precipitate. Usually-suchprecipitation occurs at =atemperature range between and 15 C. The crystals are then separated from the supernatant solution.

The next step is to saturate the nowpartially iron-free solution with hydrogen chloride gas. Such saturation is accomplished at low temperature, preferably at to -20 C., for at this temperature almost all of the iron "slightly above that at which the iron chloride was made to precipitate.

solution has now been converted into solid potassium About 95% of the titanium formerly in chlorotitanate. The potassium chlorotitanate is filtered and the precipitate dissolved in hydrochloric acid at room temperature. Subsequent cooling of the solutionand the addition of gaseous hydrogen chloride theretoresults in the recrystallization and reprecipitation of such potassium chlorotitanate.

The above recrystallizating step is not absolutely essential to the success of my process but such step does constitute part of the preferred embodiment thereof. Other methods such as an acid wash are also available to purify the chlorotitanate crystals, but the recrystallization step assures adequate purity for most purposes. This latter material especially well suited for the filtration and subsequent drying processes because larger crystals are'obtained from the hydrochloric acid solution than those present after the first precipitation of the salt from a mixture of sulfuric and hydrochloric acids. It should be understood of course that the recrystallization and/or purification of the crystals is not absolutely essential to my process. However without such steps titanium of lower quality may be produced.

. The precipitate is now centrifuged to separate it from the supernatant liquid. At this point the centrifugate contains somewhat in the order of 2 to 3% moisture in the form of concentrated hydrochloric acid solution. If such moisture is permitted to remain in and around the potassium chlorotitanate crystals a marked decrease in the net yield of titanium and a lowering of its quality will result.

The next step of the instant process is directed to the removal of such moisture without hydrolyzing the titanium compound. I have found that the rather tenaciously bound mother liquor may be efficiently and readily removed by passing a stream of dry hydrogen chloride gas through the partially dried alkali chlorotitanate, such procedure being carried out at a temperature of from 20 to 300 C. By this treatment a solid product with a water content in the order of 0.01% may be obtained.

The hydrochloric acid necessary for several steps in my process may be recovered, recycled and reused, a fact which I think is quite important from an economic standpoint.

The quantitative production of dry potassium chlorotitanate may be seen from the following example: 362 parts of ilmenite containing 50.0% TiO were mixed with 724 parts of 66 Baum sulfuric acid and the mixture rapidly heated to a temperature of 95 C. until the mass solidified. Such mass product was leached with sulfuric acid to obtain a titanium solution containing 133 grams of iron per liter. Upon cooling of this solution to 5 C. 79% of dissolved iron was precipitated in the form of iron sulfate. Subsequent to filtration the solution analyzed as follows:

Grams per liter Further cooling of the solution to --17 C. accompanied by saturation. with hydrogen chloride gas precipitated most of the remainder of the iron as ferrous chloride.

After removal of such iron, 290.4 parts of solid potassium chloride were added to the solution to form small particles of solid potassium chlorotitanate. The latter material was separated from the supernatant solution by centrifuging. Followingthis; the wet solid was redissolved in concentrated hydrochloric acid at 30 C. Large crystals of K TiCl were recrystallized and reprecipitated by saturating the hydrochloric acid solution with hydrogen chloride gas while maintaining said solution at-5 to 15 C. The recrystallized material was centrifuged and thendried in a rotary kiln at 220 C. for 3 hours under an atmosphere of hydrogen chloride gas. At the end of this time 660 parts of dried potassium chlorotitanate was obtained. i

To the best of my knowledge potassium chlorotitauate has never before been dried to a utilizable state of dry ness without, destroying its usefulness for the instant step of recrystallizing the alkali chlorotitanate makes the invention. My earlier attempts to remove the physically and chemically bound water and other oxide bearing substances from alkali chlorotitanates have given rise to various forms of hydrated titanium oxides. My discovery that the treatment of potassium chlorotitanate with dry hydrogen chloride gas effectively removes practically all of the water originally contained therein has thus given rise to this application. In the instant invention the dry potassium chlorotitanate is reduced to the free metal.

The reduction process of the instant invention is shown by the following equation:

Amen 4M T1 ZAOI 4MCl Heat where M is an alkali metal such as sodium and as will be obviousto thoseskilled in the art acts as a reducing agent, and A is an alkali metal radical.

Inthc reduction of the potassium chlorotitanate to titanium I have found that an intimate mixture with the reducing agent is quite important for as will be readily understood the reactive surfaces of the two materials must be such that reductionreadily occurs. It is for this reason that powdered alkali chlorotitanate and finely ground reducing metal is preferred. Although the exact particle size is not critical it should be understood that both types of reactant particles should have a high surface area/ volume ratio. Present particle size ranges from 1 to about 10 microns and good results are obtained when both types of particles are substantially the same size.

Although it is not absolutely essential to the utility of the instant invention I have found that the briquetting or pelletizing of the reduction mixture simplifies the material handling procedures required in these processes and also produces an end product of perhaps more desirable form than mere granules. Compression of the chlorotitanate reducing agent mixture may be used to produce a. variety of shapes, the particular shape dependent upon the equipment available to the operator for the reduction operation and the equipment used to place the crude titanium in condition for final fabrication. After reduction the titanium metal will be in substantially the same physical form as was the original pellet or briquet.

I have found that if briquets are the form in which the materials are reduced the operator must prevent the inclusion of the air in the briquet mass. Apparently air inclusion induces a variety of side-reactions which are detrimental to the production of titanium. For example. the oxygen of the air may unite with the sodium reducing agent to form various sodium oxide compounds. which of course are not useful as a reducing agent or the oxygen may directly unite with the titanium as it is formed to yield brittle titanium metal. Since titanium metal may also combine with the nitrogen present in air it is I think evident that several side reaction products may be produced. Thus not only may the air increase the cost of my process by increasing the amount of necessary reducing agent but of greater importance it may detract from the titanium pure'ness. The production of titanium-nitrogen and titanium-oxygen compounds must be prevented to as great an'extent as possible.

It shouldbe mentioned, at least parenthetically, that "even if briquets or'pellets. are-not used,'and reduction is only between, for example, granular sodium and granular alkali chlorotitanate, the air effect problem must still be prevented. 'As the dry alkalichlorotitanate isproduced it'rnay be stored in an inert atmosphere and'then reduced in' such atmosphere. The reducing agent alkali chloro- "titanate'briquets should alsobeforme'd irran inert gas "atmosphere. Most simply this entails formation'by a press in such atmosphere.

Either the die portions-of the 'press may be enclosed in a. container ofargonor the like, or the'mixture per se may be placed in a separate "air-proof pliable container which has air excluded by flushing with'argon'and' thenforming thebriquet while retaining the massin the container. 5 It is of course possibleto form a 'briquet in a vacuum but of the alter- 'nativespo'ssible this would p'robablybe the .rnost'expensive in the terms of equipmentandprocedureyhowever where the manufacturer has the vacuumequipmentavailale,'vacuum"means surrounding the'press die" may be "*more' convenient.

"Because of the 'affinity of titanium'for gases normally "presentin the atmosphereand because many of. these 'gases'either diminish or completely destroy the desirable "properties ofthe metal, as above mentioned, it is also "essential' that the reduction stage of the instant invention be carried out in either avacuum or in an inert gas atmosphere (such ashelium or argon). I consider the noble gas atmosphere to'bepreferable.

"After the material is placed in-theinert gas atmosphere the reduction may be commenced. Somewhatof "an excess' of"re'ducing"agent (up to15%)' over and above 1 the amounts stoichiometrically calculated may be utilized "to insure thecompleteness of the reducing reaction. T he reducingagents thatcan beused' include lithium, sodium, "potassium; rubidium and cesium; however for thefpurpose of the instant example the reduction "using sodium is discussed. The equation representing' thisreduction is "as 'follows:

- KzTiClu +4Na Ti 2KGl 4NaCl Heat i The KCl and NaCl are produced in the form of occluded crystals and their removal to yield purified-usable titanium is discussed below.

The potassium chlorotitanate-sodium metal mixture is heated to a-temperature of from 325 to 600 C. in the abovementioned inert gas atmosphere. Thetime required for the reduction will ofcourse somewhat depend on the temperature which is used. At a temperature of approximately 500 C. approximately 3 hours are required I to complete-the reduction. The time-heat requirements may be readily determined by the individual operator in accordance with the rateof production required and the equipment at his disposal.

When the reduction process has been completed, the

titanium has occludedtherein thefsalts prodtiedduring the process. Although there are several ways to remove the by-products I prefer leaching with dilute hydrochloric acid. It is also possible to-remove the reaction end products from the titanium metal by a vacuum distillation procedure, a procedure Well-known to those skilled 7i in this art.

'Thefollowingexamples are given to illustrate the re duction phase of -my-invention Example I to produce titanium in acontinuousmanner.

sodium chloride was separated by'watenwashingznd the titanium powder carefully dried.

' Example I] 339 grams of. anhydrous. 'K TiCl .was...thoroughly mixed in an atmosphere o-f.dry argon gas with 30 grams of lithium metal. and the mass was thenvformed .into briquets by a piston press operating. again in aprotective gas atmosphere of dry argon. Thebriquets wereheated in such argon atmosphere forfourhours at a temperature of 500 C. The resultant mixture oftitanium powder, potassium. chloride and .lithium chloride Was separated by water Washing. .The. titaniumpowder was. then carefully dried.

It is readily seen how the instantinvention is utilized After vits reprecipitation or upon itsinitial.precipitation and subsequent separation fromothe. mother liquor, the moist chlorotitanate is conveyed inan atmosphere of hydrogen .chloride. The dried material is then mixedwith the reducingagent and formed into briquets. Following this the briquets are passed through the heating chamber where reduction takes place. Briquets are continuously fed onto a belt at one end of the reduction chamber and the reduced briquets drop oif at the opposite end.

It will also be readily-seen by thoseskilled in this art that a. convenient low temperature operation is herein disclosed. Althoughreduction may take place with temperatures ranging from 325 to 600 .C. it is not essential to use-the higherextremeof this. range.

It .should be understood that although reduction in the briquet form is not essential to the instant invention this is the preferred embodiment.

The chlorotitanates of the other alkali metals namely sodium, rubidium, and cesium may also be used for the reduction to titanium. These other chlorotitauates are dried-by hydrogen chloride gas treatment and the instant process is carried out in the same manner as thereductionof the potassium chlorotitanate.

As above stated the fact that precipitated alkalichlorotitanates may be almost completely dried by heating in an atomsphere of hydrogen chloride gases is of the utmost importance to the instant invention. I know of three British patents, namely Number 645,152, 651,729 and 652,268 which issued to a nationalized Czechoslovakian corporation, Spolek Pro Chemickou Vyrobu, Narodni Podnik, which concern the production of titanium oxide pigments and show the very first steps of my process. There is. no indication however as to the method ofv removing the moisture from the alkali chlorotitanate for obviously this mosture is of no importance for pigment production. In my process on the other hand moisture is quite detrimental to the net yield of titanium and the physical properties thereof and thus the drying step-assumes the importance conceded to it. These three British patents illustrate the use of an acid' titanium ore solution followed by precipitation of the halogenotitanates. Beyond this these cases do not go and nowhere do they indicate how. titanium may be produced.

In U. S. Patent 1,437,984 issued to John W. Marden a process is described for the production of refractory metals, primarily zirconium, although titanium is also mentioned. Marden specifies the use of non-volatile salts (e. g. K ZrF of the metal to be reduced, which does not. melt or volatilize appreciably in any way at the temperature'of reaction, together with a volatile metal, ob-

taining aproduct which is non-volatile or sublimable at the temperature of the reaction (pages 1, 11, 66-73 of Marden). One suggested reaction uses K ZrF and sodium at 600 to 700 R, such sodium being molten at 700 F. No actual disclosure of other solid salts such as salts of titanium is made by Marden.

It is thus apparent that Marden teaches specifically the use of a reaction involving a liquid metallic reducing agent and a solid, non-volatile salt of a refractory metal. In contrast the instant reaction is between an extremely volatile salt and either a solid or a liquid alkalimetal. The claimed reaction has the distinct advantage that starting and end products are all solids and much lower reaction temperatures may be used. Such lower reaction temperatures are of particular industrial advantage.

It will be understood that modification and variation may be effected without departing from the spirit and scope of the instant invention.

I claim as my invention:

1. In the method of producing titanium from titaniumbearing materials whereby such materials are first converted into alkali metal chlorotitanates having physically and chemically bound water therein, the steps comprising: removing such water by subjecting said moist alkali metal chlorotitanateto hydrogen chloride gas while maintaining said chlorotitanate within the temperature range of from to 300 C.; reducing said substantially anhydrous alkali metal chlorotitanate to titanium and other reaction end products with an alkali metal reducing agent in an inert atmosphere at a temperature within the range from 250 to 600 C., and separating the titanium from such other reaction products.

2. In the method of producing titanium from ilmenite wherein such ilmenite is first convertedinto potassium chlorotitanate having physically and chemically bound water therein, the steps comprising: removing such'water by subjecting said moist potassium chlorotitanate to dry hydrogen chloride gas while maintaining said chlorotitanate within the temperature range of from 20 to 300 C.; reducing said substantially anhydrous potassium chlorotitanate to titanium and other reaction products with sodium metal in an atmosphere of helium at a tempera ture within the range of from 325 to 600 C., and separating the titaniumfrom such other reaction products.

3. The method of producing titanium from titaniumbearing material comprising the steps of: making an acidic titanium solution from such titanium-bearing material, such acidic solution being made from acids in the group consisting of sulfuric and mixtures of sulfuric and hydrochloric acids; saturating such solution with gaseous hydrogen chloride; adding to such acidic titanium solution an alkali metal chloride whereby an alkali metal chlorotitanate precipitates therein; drying said L alkali metal chlorotitanate by passing hydrogen chloride gas therethrough while maintaining said chlorotitanate at a temperature of from 20 to 300 C.; reducing said alkali metal chlorotitanate with an alkali metal reducing agent in an inert atmosphere at a temperature of from 250 to 600 C. to produce titanium and other reaction end products, and separating the titanium from such reaction products.

4. The method of producing titanium.frorn ilmenite comprising the steps of: making an acidic titanium solution from such ilmenite, such acidic solution being made from acids in the group consisting of sulfuric and mixtures of sulfuric and hydrochloric acids; saturating such acidic titanium solution with gaseous hydrogen chloride; adding to such acidic titanium solution potassium chloride whereby potassium chlorotitanate precipitates therein; drying said potassium chlorotitanate by subjecting it to dry hydrogen chloride gas while maintaining said potassium chlorotitanate at a temperature of from 20 to 300 C.; reducing said substantially anhydrous potassium chlorotitanate with an alkali metal reducing agent in a helium atmosphere at a temperature of from 250 to 600 C. to produce titanium and other reaction. end products, and separating the titanium from such reaction .bearing material comprising the steps of: making anacidic titanium solution from such titanium-bearing materials,

such acidic solution being made from acids in the group 1 consisting of sulfuric and mixtures of sulfuric and hydrochloric-acids; saturatingsuch acidic solution with gaseous hydrogen chloride; adding to such acidic titanium solution potassium chloride whereby potassium chlorotitanate precipitates therein; drying said potassium chlorotitanate by. subjecting it to dry hydrogen chloride gas while maintaining said potassium chlorotitanate at a temperature of from 20 to 300 C.; reducing said substantially anhydrous potassium chlorotitanate with an alkali metal reducing agent in a helium atmosphere at .a temperature of from 250 to 600 C. to produce titanium and other reaction end products, and separating thetitaniumfrom such reaction products.

7. The method of producing titanium from ilmenite comprising the steps of: making. an acidic titanium solu tion from such ilmenite, such acidic solutionbeing made from acids in the group consisting of sulfuric and mixtures of sulfuric and hydrochloric acids; saturating such acidic titanium solution with hydrogen chloride gas; adding tosuch acidic titanium solution potassium chloride whereby potassium chlorotitanate precipitates therein; dissolving the said potassium chlorotitanate precipitate .in hydrochloric acid; reprecipitating said potassium chloro titanate by treating said hydrochloric acid solution with hydrogen chloride; drying said potassium chlorotitanate by subjecting it to dry hydrogen chloride gas, while maintaining said potassium chlorotitanate at a temperature of from 20 to 300 C.; reducing said substantially dry 1 potassium chlorotitanate with an alkali metal reducing agent in an inert atmosphere at a temperature of from 250 to 600 C. to produce titanium and other reaction end products, and separating the titanium from such reaction products.

8. The method of producing titanium from titaniumbearing material comprising the steps of; making an acidic titanium solution from such titanium-bearing material, such acidic solution being made from acids in the group consisting of sulfuric and mixtures of sulfuric and hydrochloric acids; saturating such solution with gaseous hydrogen chloride; adding to such. acidic titanium solution an alkali metal chloride whereby an alkali metal chlorotitanate precipitates therein; dissolving and recrystallizing said alkali metal chlorotitanate; mechanically drying said alkali metal chlorotitanate whereby a portion of its water content is removed; completing the drying of said alkali metal chlorotitanate by subjecting it to dry hydrogen chloride gas while maintaining said alkali metal chlorotitanate at a temperature of from 20 to 300 C.; reducing said substantially dry alkali metal chlorotitanate with an alkali metal reducing agent in an inert gas atmosphere at a temperature of from 250 to 600 C. to produce titanium and other reaction end products, and separating the titanium from such reaction products.

References Cited in the file of this patent UNITED STATES PATENTS Bousquet et al June 30, 1942 

8. THE METHOD OF PRODUCING TITANIUM FROM TITANIUMBEARING MATERIAL COMPRISING THE STEPS OF: MAKING AN ACIDIC TITANIUM SOLUTION FROM SUCH TITANIUM-BEARING MATERIAL, SUCH ACIDIC SOLUTION BEING MADE FROM ACIDS IN THE GROUP CONSISTING OF SULFURIC AND MIXTURES OF SULFURIC AND HYDROCHLORIC ACIDS; SATURATING SUCH SOLUTION WITH GASEOUS HYDROGEN CHLORIDE; ADDING TO SUCH ACIDIC TITANIUM SOLUTION AN ALKALI METAL CHLORIDE WHEREBY AN ALKALI METAL CHLOROTITANATE PRECIPITATES THEREIN; DISSOLVING AND RECRYSTALLIZING SAID ALKALI METAL CHLOROTITANATE; MECHANICALLY DRYING SAID ALKALI METAL CHLOROTITANATE WHEREBY A PORTION OF ITS WATER CONTENT IS REMOVED; COMPLETING THE DRYING OF SAID ALKALI METAL CHLOROTITANATE BY SUBJECTING IT TO DRY HYDROGEN CHLORIDE GAS WHILE MAINTAINING SAID ALKALI METAL CHLOROTITANATE AT A TEMPERATURE OF FROM 20* TO 300*C.; REDUCING SAID SUBSTANTIALLY DRY ALKALI METAL CHLOROTITANATE WITH AN ALKALI METAL REDUCING AGENT IN AN INERT GAS ATMOSPHERE AT A TEMPERATURE OF FROM 250* TO 600*C. TO PRODUCE TITANIUM AND OTHER REACTION END PRODUCTS, AND SEPARATING THE TITANIUM FROM SUCH REACTION PRODUCTS. 